The present invention generally relates to a molluscicides, and more particularly to a molluscicide having an effective and an environmentally safe low dose mollusc killing active ingredient.
Slugs and snails Terrestrial Gastropod Molluscs are capable of causing extensive damage to Horticultural Ornamental plants and Agriculture food crops. They are omnivorous, consuming leaves, bulbs, tubers, fungi, lichens, algae and animal matter. Agricultural food crops extensively damaged by terrestrial molluscs include leafy vegetables, green beans and strawberries. Fruit and fruit trees and the like are extensively damaged, as is horticultural gardening and ornamental plants. Animal crops such as hay and clover are also extensively damaged by molluscs. Tests have shown that a slug or snail can consume its own weight in food materials in a matter of days.
Slugs and snails are closely related members of the phylum mollusca. Snails have a large external shell used for protection against predators and adverse climatic conditions. However, snails require a living environment containing large quantities of calcium containing materials, including lime (CaCO.sub.3). Calcium containing materials are necessary for the snail to develop its shell. Therefore, most snails are found in areas having soil rich in calcium.
Slugs do not have an external shell and do not require calcium rich soil to survive. Although slugs are capable of burrowing into the earth for food and shelter, they are vulnerable to desiccation and death in open and unshaded areas. Therefore slugs primarily subsist in high moisture climates. In the United States, the Pacific Northwest provides moist condition conducive to slug survival and propagation.
Slugs and snails, if uncontrolled can propagate at a rapid rate, causing enormous horticultural and agricultural damage. Because they are semi-nocturnal, they often avoid capture by predators. Most slug and snail predators, including birds, actively feed during day light hours only. The agricultural problems caused by slugs and snails were recognized and reported in the early years of the twentieth century. For example, the state of Oregon recognized the potential damage from slug infestation in 1911. In that year, Oregon initiated studies involving slug control. Work done through the year 1919 resulted in a method of controlling slug using a composition having an attractant (lettuce) combined with calcium arsenate, an environmentally hazardous poison.
Nearly 15 years later, another chemical molluscicide was discovered which is still in use today. This substance is metaldehyde which is a polymer of acetaldehyde with the empirical formula C.sub.8 H.sub.16 O.sub.4. Metaldehyde is formed by the polymerization of four to six acetaldehyde molecules. Metaldehyde has a characteristic vinegar-like odor which is highly attractive to slugs and snails. By either ingestion or external contact, metaldehyde causes a brief period of paralysis followed by stimulation of the mucus-secreting glands in the slugs or snails. Such stimulation of the mucus secreting glands results in the production of large quantities of viscid slime. Excessive slime production, in combination with desiccation by the sun during daylight hours, causes death by dehydration.
However, metaldehyde has numerous safety and efficacy problems. First, metaldehyde is toxic to both humans and animals. In most commercial formulations, 2-4% by weight metaldehyde is used. This amount is potentially harmful when used around humans and animals.
Furthermore, the efficacy of metaldehyde as a molluscicide is limited. It is only effective under certain environmental conditions. For metaldehyde to function, dry, warm and sunny conditions must be present. These conditions enhance the desiccating effects caused by metaldehyde. However, when moist, overcast conditions exist, snails and slugs can overcome the desiccating effects of metaldehyde, by excreting the material from their bodies in a matter of days. Without enhanced desiccation by the sun, the effectiveness of metaldehyde is limited. In fact, tests indicate that slugs and snails, after intoxication with metaldehyde, will actively seek shaded areas and soil high in moisture to overcome the effects of metaldehyde.
Metaldehyde also has limited effectiveness in killing juvenile slugs and snails. The scientific mechanism behind this problem is presently unknown. Finally, metaldehyde is relatively expensive, selling for approximately $3.50 per pound. Such cost can be prohibitive in a large agricultural operation.
In view of the above described shortcomings of metaldehyde research has been directed toward finding new molluscicide compositions. For example, U.S. Pat. No. 3,090,723 Pastac involves a method of combatting molluscs in which metaldehyde is combined with a halogenated aldehyde derivative. Preferred halogenated aldehyde derivatives include chloral ammonia, chloral hydroxylamine, trichloracetaldoxime, arabo-chloralose, glucochloralose, mannochloralose, galacto-chloralose, chloralurethane, chloralformamide, monochloralcarbamide, and dichloralcarbamide. The Pastac composition preferably uses 0.3-3% metaldehyde and 1-3% halogenated aldehyde derivative.
U.S. Pat. No. 3,284,296 to Freiberg involves a molluscicide in the form of trialkyl tin compound having the following basic formula: EQU (lower alkyl).sub.3 --Sn--XR
In this formula, the lower alkyl group contains from 1-6 carbon atoms. X is selected from the group consisting of oxygen and sulfur, and R is selected from the group consisting of phenyl, naphthyl, and quinolyl groups and these groups substituted with, for example, methyl, ethyl, n-pentyl, 2-methylbutyl, n-hexyl, 2-methylpentyl, and 2,2-dimethylpropyl.
Notwithstanding the above compositions, a need exists for an effective environmentally safe and economical molluscicide. The present invention represents a new and improved molluscicide composition satisfying this need, as described herein below.